The number of severely obese 2- to 4-year-olds enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) increased to slightly more than 2 percent of all kids from 2000 to 2004, but it then decreased over the next decade to slightly less than 2 percent.

Though a small drop, the trend was seen among all ethnic and racial groups living throughout the nation, the researchers noted.

"Our findings indicate recent progress in reducing the prevalence of severe obesity among young U.S. children enrolled in WIC," said lead researcher Dr. Liping Pan, an epidemiologist at the U.S. Centers for Disease Control and Prevention.

Obesity rates in children remain high, and those with obesity and severe obesity face significant health and social challenges, such as asthma, sleep apnea, bone and joint problems, high blood pressure and type 2 diabetes, she said.

"These lifelong health risks associated with severe obesity during early childhood indicate the importance of preventing and identifying severe obesity as early as possible," Pan said.

Differences in genetic, behavioral and environmental factors across years may have contributed to the increases and decreases in the prevalence of severe obesity, Pan said.

In addition, changes in WIC benefits might also have influenced the recent declines in obesity and severe obesity.

"The WIC food packages were revised in 2009 to promote fruits, vegetables and whole-wheat products, include more variety of healthy food options, support breast-feeding and provide state agencies with greater flexibility in prescribing foods to accommodate cultural food preferences," she said.

Recommendations and activities from the CDC and strategies from the U.S. Institute of Medicine to prevent and manage childhood obesity also may have contributed to the modest declines in severe obesity, Pan said.

The report was published online Jan. 8 in JAMA Pediatrics.

"The last time we got news about severe obesity among young children in the U.S., that news was all bad," said Dr. David Katz, director of the Yale-Griffin Prevention Research Center and president of the American College of Lifestyle Medicine. "But no one should mistake this reassuring update for good news."

Except for the rare endocrine or genetic conditions, childhood obesity is entirely preventable. "That nearly two out of every 100 children in WIC are subject to the adversities of severe obesity is a national disgrace," Katz said.

For instance, he said that Americans are too willing to overlook the perils of a food supply that he described as willfully engineered to be addictive. They're also willing to recognize junk food as a food group and to mortgage the future health of children for the sake of corporate profits, he said.

"We may be thankful for a slight improvement in these trends," Katz said. "But that there are trends in severe childhood obesity worth tracking in the first place is testimony to a societal failure for which we should all hold ourselves accountable."

For the study, the researchers -- from the CDC and the U.S. Department of Agriculture's Food and Nutrition Service -- collected data on nearly 23 million 2- to 4-year-olds from all the states who were enrolled in WIC from 2000 to 2014. Specifically, the researchers looked for the prevalence of severe obesity among these children.

They found that the prevalence of severe obesity decreased from 2.12 percent to 1.96 percent from 2000 to 2014.

The findings refer only to children in the WIC program and may not be representative of all low-income children because only about half of young children eligible for WIC are enrolled in the program, Pan said.

Nutritionist Samantha Heller said that "the nutrition education, improved access to fruits and vegetables and support provided by programs like WIC go a long way in helping families make healthier choices."

That's especially true, she said, "in a world where we are bombarded with highly effective marketing campaigns targeting kids for fast and junk foods, sweets and other unhealthy foods." Heller is a senior clinical nutritionist at New York University Medical Center in New York City.

Parents need to take charge of their kitchens and not be swayed by the popularity of highly processed foods, she said.

They can save time and money and create healthier meals by planning ahead, cooking more at home, shunning fast and junk foods, ditching sugar-sweetened beverages and getting themselves and their children to be physically active, Heller said.